Look at them, like two cats who just stepped off the L train from Williamsburg, Brooklyn. You could have guessed that Jon French and Jack Ellis, with their speak-easy-inspired attire, dabble in mixology. The “where” part is harder to pin down.

These guys run a cocktail pop-up — in May at the Anchored Ship coffeehouse in Ballard, in July, another ’hood … somewhere. They specialize in coffee cocktails, which seems like a contradiction, mixing a stimulant (caffeine) with a depressant (alcohol). Hence its name, High Low Pop-Up Bars.

The concept has generated enough buzz that they’re taking their pop-up across Seattle this summer.

Anyone who barhops knows that the booze-and-beans combo, other than an Irish Coffee, hasn’t been popular.

French, who manages the Anchored Ship during the day, thinks he knows why: Most coffee cocktails aren’t that good, relying on a pot of coffee when they should be made with espresso shots. “Getting a great extraction (from the bean) will make or break a cocktail,” said French. And that can only be achieved by making the espresso shot to order, not pre-batch like other cocktail ingredients behind the bar.

“The hard part is the temperature and the texture have got to be right,” he said. “You got to chill down (the espresso) without losing the extraction. And getting the right amount of ice” in the cocktail.

One of their concoctions, “The Ship,” takes a robust Italian liqueur (with rhubarb, clove and orange notes) and rounds it out with some floral and citrusy notes from an Ethiopian espresso, Yirgacheffe, along with a dash of chocolate bitters and zest of grapefruit.

If you blindfolded me, I would have thought this layered and nuanced drink had six or seven ingredients.

For one, these time-consuming spiked espressos are hard to pull off at a high-volume drink den, and most bartenders don’t have a barista background.

But in our hyper-caffeinated city, it may have a place at the bar. Opened last month on Capitol Hill, Corretto bar restaurant is dedicated to this brew-to order coffee cocktail concept.

At his pop-up, currently on weekends at Anchored Ship coffee shop, along the barhopping strip in Ballard, French said he was surprised to find patrons drinking their brews, even at midnight. The menu will expand with three coffee cocktails along with virgin espressos and vermouth-based drinks.

To keep cost down, French borrowed the pop-up model from prep cooks and circumvented the state’s high booze tax by using fortified wine instead of vodka or whiskey.

French found a business partner in Ellis, a former barista in Dallas. They struck up a friendship after Ellis started hanging out at his coffee shop after his day job at Amazon. “I drink two maybe three cups a day. Then I go to Anchored Ship and drink another two cups,” Ellis said.

In French, he found someone who thought that was perfectly normal.

Mixing espresso with vermouth is common in Italy. It’s not that different from how we look at coffee, Ellis said. “It’s like a latte where you add milk and espresso. Or coffee with cream and sugar. People add those flavors to round it out, to make it more robust.”

High Low Pop-Up Bars currently held at Anchored Ship coffeehouse, 5306 Ballard Ave. N.W., on Friday and Saturday, 8 p.m.-1 a.m. in May (highlowpopupbars.com).

Tan Vinh: 206-515-5656 or tvinh@seattletimes.com; on Twitter: @tanvinhseattle. Tan Vinh is a features writer for the Seattle Times. He hikes and drinks for a living, though he never does both at the same time. At least not while on the clock.